I'm not saying this is the best way, but I sold my LEAF 24 to Drive-Green.co.uk (in October 2018), I sent them an email, load of photos etc, they made an offer, I haggled, we came to an agreement, they sent a deposit. They then arranged collection a few days later with a simultaneous bank transfer so I had cleared funds in my bank account before the car drove away. It was a refreshingly painless transaction. It's worth noting that I emailed several 'EV' specialists but Drive Green made the best offer by far and came very close to the private sale value. My LEAF was battery owned, I think this made the car simpler to trade. Good luck 
